Some bird bones are hollow rather than honeycombed. The hollow bones mostly contain air sacs. The replacement of bone marrow with air sacs is properly understood as an adaptation that ________.
1) reduces the weight of the bird
2) facilitates flight
3) eliminates the functions of bone marrow
A) only 1
B) only 2
C) only 3
D) 1 and 2
E) 1, 2, and 3

Question

Quizplus · Accepted Answer

The hollow bones reduce the weight of the bird, making it easier for them to fly. However, they do not eliminate the functions of bone marrow completely, as birds still need to produce red blood cells, which are formed in the spleen and liver rather than the bone marrow. Therefore, choice 1 and 2 are correct. Choice 3 is incorrect as bone marrow still has some functions in birds.

Some Bird Bones Are Hollow Rather Than Honeycombed